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Extraterrestrial life


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For as long as humans have looked up at the stars, we have pondered a very intricate and nostalgic question, "Are we alone?"


The answer to this question has been debated for many centuries. Most skeptics conclude that if there is life out there, it is certainly not multicellular, eukaryotic life. However, we often forget the fact that there are several eukaryotic organisms that are on our planet that brave very harsh, and somewhat, inhospitable conditions. Does it seem so unlikely that there are creatures elsewhere in the universe that could use other metals and gases besides carbon and oxygen? Some beings elsewhere may use silicon and argon contrary to our own genetic makeup. They may have no DNA, but only RNA. This seems to be more of an abstract concept that originated in science fiction, but do not forget that many innovations such as the shuttle and the internet were once considered nothing more than simple science fiction.


There may be creatures that float above gas giants, taking in gases that suspend them above the intense gravity. These beings would constantly be afloat, and require nothing more than gas to sustain themselves. This idea has been pondered by many great scientists in the past one hundred years, but the question is, is it possible? Based on how life works here on earth, it seems completely possible that life may be able to live in the clouds. For example, we have found strange creatures in our atmosphere that float above the clouds. They may be prokaryotic, yet they show that with evolution, it is possible that complex life could form above the clouds.


Extraterrestrials may also be able to live on worlds that seem either too hot, or too cold to support life. Worlds that are covered in ice and have liquid nitrogen oceans may be able to support life that has adapted to these harsh conditions. There may be life that lives on rocky worlds that have oceans of lava, these organisms would live off of the minerals in the rock. Earthworms are able to eat soil, which contains valuable nutrients; imagining complex life on a lava planet would have the same concept: creatures that are made of segments that would be able to bury underground during radiation bursts, and eat rocks that contain minerals.


An even more abstract thoughtis for creatures that live on lush and hospitable worlds, like our own planet earth. We may be very surprised to find that life evloved very differently than we could ever imagine. Creatures on lush worlds may be hardly what we expected, such as creatures that are a whole new division of life that we do not know about. These creatures may live off of plants that are poisonous to humans. There may also be extremely evolved predators that can simply fly, walk, and swim with complete ease. These creatures would easily be able to capture their prey, unless, of course, the prey had a form of defense, such as a tail or claws.


I would like to know everybody's views of extraterrestrial life, please reply and share your own opinions on the subject.

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The answer to this question has been debated for many centuries. Most skeptics conclude that if there is life out there, it is certainly not multicellular, eukaryotic life.


The premise is faulty. I really doubt that applies to most or even many people interested in this subject. First of all. eukaryotic life is highly specific and based on terrestrial life. There are no meaningful predictions about what it could be elsewhere.

What is being assumed that there is likely not very complex life within our solar system. But as all everything about extraterrestrial life remains speculative.

With regards to silicon the best counterargument is that carbon is just more versatile. Under most conditions that we know life exists metabolic activities are easier to handle. For example during metabolizing carbon you can end up with carbon dioxide which can be eliminated passively from cells. Silicon oxide (being solid under known physiological conditions) would require some kind of export system, which is less effective.

Carbon would simple have an edge there.

With regards to DNA and RNA, again there is a specific extrapolation of terrestrial life. Note that one hypothesis posits that proto-life on Earth was potentially based on RNA.

Temperature limits have a basis on thermodynamics which makes life less likely above certain extremes and so on.


In other words, many of these speculations, some with more, some with less merit have been around for a long time, but in the absence of any research and evidence it will remain just that. Speculations.

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To make CharonY's point in the words I prefer to use about this issue: It is dangerous to extrapolate from a sample size of one.


Whether we discover we are the only life in the universe, or that life is abundant and ubiquitous, or anywhere in between, the discovery will be surprising.

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  • 2 weeks later...

I'm going to agree with CharonY on those points... as for my own opinion:


I'm no astronomer, so I don't know exact numbers of how many stars and planets are out there; but I imagine from a numbers-standpoint there is definitely extraterrestrial life out there.


I think the sole most important thing for "life" to exist is self-replication. Nature also prefers the efficient, so the most efficient self-replicators will proliferate, and the most of efficient of those will go on, and so forth.


Then you have physical factors that affect how these self-replicators are selected. Physical effects such as gravity, temperatures, and chemical composition of planets (or whatever environment these self-replicators might arise), are the factors that determine the "characteristics" of these self-replicators. So yes, if you had a planet full of rock, in which some self-replicating molecule (maybe even atom) arose, then you might very well see organisms that "eat" rock due to its abundance. These physical 'factors' really limit what kind of life you might find, which is actually very good if we're trying to picture what kind of life might exist, because it narrows the possibilities. So even if you have a planet full of rock, the rock may not be a suitable energy source so perhaps life would not arise on its own there for an infinitely large amount of time.


Before you can extrapolate to very extraordinary life, I think it's necessary to start with the simplest of them all. The simplest organisms are often the most efficient, and from simple organisms you can determine what kind of complex extraterrestrial life you might find. And these simple organisms are efficient because nature prefers the efficient, so conversely if we understand nature (the sciences) we could understand how simple organisms might arise, and ultimately how complex life might arise.


As Ophiolite said (I'm going to kind of.. extrapolate from what he said :P), if we only understand physical laws as they govern Earth, we'd only understand how life could arise on Earth. So what we really need to do is understand the physical laws of other planets, star systems, etc.

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Doesn't it all come down, in the end, to numbers.


Our Solar System contains eight planets. One of these, the Earth, definitely contains life.


We can't be sure about the others - Mercury seems guaranteed lifeless, Venus almost certainly the same. Mars - perhaps a 1 in 10 chance of current life as microbes.


As for the outer planets Jupiter, Saturn, Uranus, Neptune - they're just freezing-cold balls of poisonous gas. Unless - as Jayhawk points out in excellent post#1 - they contain floating creatures in a warm kind of mesosphere. However so far, we've no evidence of that. Our probes to Jupiter and Saturn have shown no indications of life. OK - there might be life in hypothetical sub-surface oceans of Europa, or other satellites of the outer planets. But as yet there's no proof - it's just speculation.


So probably the Solar system is a dud as far as life is concerned - except for the Earth.


But what of it? The Milky Way galaxy contains at least 100 billion stars, and some of those stars have planets. Researches in the last twenty years show that's true. So there's likely to be another life-bearing Earth-equivalent in our galaxy.


Even if there isn't - does it matter. Suppose each galaxy contains only one planet with life. The Universe contains what, 50 billion galaxies? So even at a rate of only one life-bearing planet per galaxy, there'd be plenty of life spread through the Universe.


Therefore doesn't it seem, from the numbers alone, that life - at least in simple forms - ought to be fairly common in the Universe.

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I am betting Enceladus will be the first object to have life confirmed as existing inside, it spews out geysers of water ice that have signs of biology and these ice crystals may be contributing to the rings of Saturn.




In May 2011 NASA scientists at an Enceladus Focus Group Conference reported that Enceladus "is emerging as the most habitable spot beyond Earth in the Solar System for life as we know it".[19]


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Therefore doesn't it seem, from the numbers alone, that life - at least in simple forms - ought to be fairly common in the Universe.

This may be the tenth time I have posted these words. It is foolish to extrapolate from a sample size of one.


We do not know the precise conditions and route by which life arose, therefore we cannot know what the probability of the event is. Therefore any speculation is exactly that - a guess. A guess constructed on assumptions, hand waving estimates and further guesses.

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